Numerous processes are in use and have been proposed for the conversion of organic compounds and feedstocks to more valuable organic compounds and more valuable feedstocks, for use in the organic chemical and petrochemical industries, particularly organic compounds and feedstocks derived from petroleum sources.
One promising approach to such conversion has been the oxidative conversion of organic compounds to other organic compounds. However, in many cases, such oxidative conversion processes are not commercially viable, primarily because they are energy intensive, conversions of the feedstock are low, selectivity to the desired compounds is low and such processes cannot be utilized in a continuous manner. In most of such processes the feedstocks are contacted with a solid contact material. However, there is a difference of opinion among workers in the art concerning the nature of such processes, and, particularly, the function of the contact material and the manner in which such function is performed. For example, workers in the art have, at one time or another, suggested that the function of the contact material involves a purely physical phenomonen, an adsorption-desorption process, either of atomic or molecular oxygen, either on the surface or occluded within the solid material, oxidation-reduction utilizing multivalent metals capable of oxidation-reduction, adsorption and desorption of the organic materials on the solid materials, a free radical mechanism, etc. Consequently, the solid materials utilized are referred to variously as "contact materials", "promoters", "activators" and "catalysts". Accordingly, in order to avoid functional categorization, the terms "solid contact material" or "solid contact materials" will be utilized in the present application.
Since many processes of the prior art are based on the theory that the contact materials function via adsorption-desorption of oxygen, oxidation-reduction, etc., such processes are operated in a cyclic manner by passing an oxidizing gas over the contact material, then contacting the feedstock with the oxygen-containing contact material, and, thereafter, reactivating or regenerating the contact material by again passing an oxidizing gas thereover. Such processes thus require undesirably high temperatures, are energy intensive, since the exothermic and endothermic reactions occur separately, equipment costs are high, because of the necessity for rapid cycling, and the contact material's useful life is comparatively short.
From the above, it is quite clear that the suitability of contact materials for the oxidative conversion of organic compounds is unpredictable. It is, therefore, highly desirable that improved contact materials for such use be developed, and that improved processes utilizing such contact materials be provided, particularly processes which lower the temperatures necessary, lower the energy requirements, are capable of being carried out in a continuous manner, extend the useful life of the contact material, improve the conversion of the feedstock and improve the selectivity to the desired products.
Of the various feedstocks for the organic chemical and petrochemical industries, olefins, such as ethylene and propylene are of particular interest and have become major feedstocks. Of these, ethylene is by far the more important chemical feedstock since the demand for ethylene feedstocks is about double that for propylene feedstocks. Consequently, there is a definite need for materials and processes for the conversion of relatively inexpensive feedstocks to ethylene. At the present time, ethylene is produced almost exclusively by the dehydrogenation or pyrolysis of ethane and propane, naptha and, in some instances, gas oils. About 75% of the ethylene is produced at the present time by steam cracking of ethane and propane derived from natural gas, since natural gas contains from about 5 volume percent to about 60 volume percent of hydrocarbons other than methane, with the majority being ethane. However, relatively severe conditions, particularly temperatures in excess of about 1000.degree. C., are required and, as indicated, such processes are highly energy intensive. In order to reduce the severity of the conditions, particularly temperature, numerous proposals to promote pyrolytic reactions have been made. While some of these processes do, in fact, reduce the severity of the conditions, the conversion of the feedstock and the selectivity to ethylene are still quite low. Of particular interest in this phase of the art, are the oxidative dehydrogenation of alkanes, particularly alkanes having from 2 to 7 carbon atoms, and, still more particularly ethane, and the oxidative conversion of methane to ethylene. However, many of the processes for oxidative dehydrogenation and oxidative conversion of methane, which have been proposed, are subject to some or all of the previously mentioned deficiencies.
More recently, novel contact materials have been discovered which increase the conversion and selectivity to desired products in methods for the oxidative conversion of feed organic compounds to product organic compounds. While this discussion and the discussions hereinafter, at times, refer to certain components of these contact materials as "base materials" and others as "promoters", it is to be understood that these designations are made as a matter of convenience in identification, rather than by way of function. In all instances, the base materials, as well as the promoters, are active components of the contact material and the base materials are not inert "bases" or "carriers", as the designation sometimes indicates or implies.
Commonly assigned U.S. patent applications Ser. Nos. 713,653, 713,756 and 713,674, all filed on Mar. 19, 1985, relate to the use of Group IIA materials as base materials. Likewise, U.S. patent application Ser. No. 713,673, filed Mar. 19, 1985, relates to zinc as a base material. U.S. patent application Ser. No. 742,340, filed June 7, 1985, refers to titanium as a base material. U.S. patent application Ser. No. 742,337, filed June 7, 1985, refers to Lanthanum Series metals as base materials. U.S. patent application Ser. No. 945,129, filed Dec. 22, 1986 relates to certain combinations of these base materials. Each of these base materials is preferably promoted with a Group IA metal promoter. U.S. patent application Ser. No. 742,339, filed June 7, 1985 (now U.S. Pat. No. 4,620,057), relates to contact materials comprising cobalt, a metal selected from the group consisting of zirconium, zinc, nickel, indium, lead and bismuth, phosphorous, at least one Group IA metal and oxygen. Application Ser. No. 742,338, filed June 7, 1985, relates to the use of Group IA and/or Group IIA metal phosphates as contact materials. U.S. patent application Ser. No. 945,223 filed Dec. 22, 1986 relates to the use of a contact material comprising cobalt, at least one Group IA metal, silica and oxygen. All of the above-mentioned contact materials can also be further enhanced by the addition of a halogen thereto. In accordance with U.S. patent application 742,335, filed June 7, 1985, the halogen can be supplied by at least intervally adding the halogen or a halogen precursor to the reaction zone. The entire contents of each of these patent applications and patents are incorporated herein by reference.
While the use of the above-mentioned contact materials and techniques have greatly enhanced the conversion of the feed organic compounds and the selectivity to desired product organic compounds, still further improvement, in both categories, is particularly desirable.